1. Field of the Invention
The invention relates to a shoe which has an ergonomic foot pad, more particularly to an ergonomic foot pad having a heel part with a concave surface conforming to the contour of the wearer""s heel.
2. Description of the Related Art
Shoes manufactured by using lasts having planar bottoms generally do not conform to the contours of wearers"" feet and thus are insufficient to contact and support all parts of the bottom surface of the wearer""s foot. Usually, stress concentration due to the weight of the wearer""s body occurs at the foot palm and heel of the wearer which press the shoe sole. Especially, injury can be caused to the mid part of the wearer""s heel in case of prolonged wearing of the shoe.
It is known to use a last with a bottom convex face conforming to the bottom of the wearer""s foot in manufacturing a sandal. Such a last is shown at (2) in FIGS. 1 and 2 and has a convex bottom face 2A at the bottom of the heel thereof. A sandal 4 made thereby is shown in FIG. 3 and has a foot bed 41 which is received fittingly in a concave top face (not shown) of an outsole 42. The concave top face of the outsole 42 conforms to the contour of the convex bottom face 2A of the last 2 since the outsole 42 is molded by using a mold incorporating the last 2. Since the flexible foot bed 41 follows the contour of the concave top face of the outsole 42, it can contact and support all parts of the convex bottom surface of the wearer""s heel so that the stress occurring at the bottom of the wearer""s heel can be distributed evenly on the foot bed 41, thus eliminating the problem of stress concentration. However, the production of outsoles having concave surfaces conforming to wearers"" feet requires molds which are different from those used to produce outsoles having no such concave surfaces. Since molds used to manufacture outsoles are usually expensive, costs are increased considerably when producing the above two types of outsoles using different molds. In order to save costs, it is desirable that different kinds of shoes can be made by using common outsole molds.
It is usual to provide a shoe with a reinforcement piece, such as a counter or stiffener, at the heel section of the shoe. For example, U.S. Pat. No. 4,622,764 discloses a molded shell made of a rigid material, such as a rigid plastic or metal, so as to reinforce the rear portion of the shoe. The molded shell is placed at the outer side of an upper and is assembled with the upper after the upper is lasted. Since this molded shell has planar top and bottom faces in a heel region, it is insufficient to support all surface areas of the wearer""s heel.
An object of the present invention is to provide a shoe with an ergonomic foot pad which has a concave support face conforming to the contour of the wearer""s heel but can be manufactured at a reduced cost as compared to an outsole.
Another object of the invention is to provide a shoe with an ergonomic foot pad which has a heel-conforming concave support face and which can be incorporated into an outsole having no heel-conforming concave surface.
According to the present invention, a shoe comprises: an outsole having a lower tread face, an upper face, and a peripheral flange projecting upward from the upper face and confining a cavity above the upper face, an ergonomic foot pad disposed inside the cavity and cemented to the outsole; an upper connected to the foot pad, the foot pad including a heel part which has a bottom face connected to the outsole, and an upward flange projecting upward from a periphery of the heel part and making a U-shaped turn around the heel part, the heel part further having a concave upper surface which is opposite to the bottom face, the concave upper surface extending gradually upward and outward in a direction from a mid part of the heel part to a top end of the upward flange, the upward flange having an outer surface which forms a corner with the bottom face, the concave upper surface having a curved face opposite to and extending along the corner, the heel part having, between the bottom face and the concave upper surface, a thickness which decreases gradually from the upward flange toward the mid part of the heel part.